Axial flow blower



Nov. 18, 1952 M..| MAurz AXIM. FLOW BLQWER .Filed May 21;. .1951

JNVENTaR. Max L Maltz Patented Nov. 18, 1952 AXIAL FLOW BLOWER Max L. Maltz, Los Angeles, Calif., assignor to American Electro-Mechanics, Pasadena, Calif., a corporation of California I Application May 21, 1951, Serial No. 227,335

(Cl. 23o-117) 2 Claims.

This invention relates generally to an axial ow fan of improved construction, and in particular to a blower of high 'eliiciency and small size, adaptable for the cooling of electronic apparatus mounted in enclosed cabinets.

Recent developments in the field of electronics include complicated multicircuit electronic devices, which for purposes of convenience in handling and storage have been enclosed in relatively small cabinets. The space required for the circuits is reduced to a minimum by overlapping the circuits and compactly arranging them within one another. A serious limitation to which the space required for the circuits may be reduced lies in the fact that there must be sufficient space within the cabinet to allow cooling of the circuits by the air therein contained and surrounding the circuits. Electronic circuits are subject to considerable heating due to the ultra-high frequency currents utilized therein and their effect on electronic components in the circuit, In order to prevent excessive and injurious increases in temperature it is necessary to keep the ambient temperature of circuit surroundings at a minimum. The most feasible and least expensive method of doing this is to provide means whereby a draft of cooling air is drawn from outside the cabinet and directed over the heated electronic components to withdraw heat. Vents may be provided for the emission of air from the cabinet after it has passed over the heated components of the electric circuit.

A primary object of this invention is to provide a small, light Weight and ellcient high-speed fan mounted in a port provided therefor in the cabinet Wall of an electronic machine and adapted to draw air into the cabinet and direct it over the heated components of the electronic circuit.

A further object of this invention'is to provide an axial flow fan and duct, the duct having a minimum of resistance to the free flow of air in-v duced by the fan.

Still a further object of this invention is to utilize a conical fan hub to provide and maintain a continuously diverging flow of air.

Still another object is to provide an improved motor fan unit of compact design and high eiliciency.

Referring now to the drawing:

Figure 1 is a front view of an axial flow blower constructed in accordance with the present invention;

Figure 2 is a side view of the axial flow blower;

Figure 3 is a back view of the blower;

Y Figure 4 is a longitudinal section of the blower taken on line 4-4 of Figure 2; and

Figure 5 is a perspective View of the improved multi-bladed impeller utilized in the present invention.

Referring again to the drawing, and particularly to Figures 1 and 2, an axial flow motor fan unit constructed in accordance with the present invention is indicated generally by the reference character I0 and is seen to comprise basically a cylindrical duct I2, a motor casing I4 Within duct I2, and an impeller I3l driven by electric motor I5 positioned within casing I 4. A flat rigid flange 2I formed at the front or intake end of duct I2 and extending outwardly from the peripheral edge thereof is utilized to affix the fan unit to a conventional cabinet wall, a portion of which is indicated by the reference character I I. Referring to Figure l, the inside surface of the ange 2| is seen to abut the outside wall of th-e cabinet around a suitable aperture through which the duct I2 extends.

Flange 2| is formed with a, plurality of equally spaced holes 22 and adapted to receive screws or bolts to secure the blower unit rigidly to the cabinet wall.

The back or discharge end of duct I2 has three deep arcuate cutaway recesses or serrations cut therein at equal intervals and three support fins or webs I8 extend perpendicularly inwardly toward the longitudinal axis of the duct. Each of the fins I8 is positioned on the duct wall midway between adjacent arcuate serrations at the points of maximum duct wall length. The motor casing I4, generally cylindrical in shape, is rigidly supported concentrically in duct I2 on supporting fins I8.

Referring to Figures 3 and 4, motor casing I4 is seen to comprise a cylindrical side wall 23 carrying rigid support ns I8, and integral therewith in a preferred form, a detachable rear wall 24, and a front wall 21. Rear wall 24 is sized to flt snugly Within wall 23 except for an enlarged peripheral shoulder 24a which abuts the end of Wall 23. Front wall 21 is formed on its inner side with a reduced diameter circular shoulder 21a which forms a seat for the front end of the wall.

Motor proper I5 is positioned immediately adjacent front wall 21 of the casing and is suitably xedly secured thereto. It includes a stator 28 rigid with wall 21, an end casing 29, and an unshown armature the shaft 32 of which is mounted suitably in unshown bearings and which extends forwardly through front wall 21. A pair of elongated screws 26 with their heads recessed in rear Wall 24 extend to motor end casing and exert a` forceto draw the motor toward the end wall, and' in so doing to draw both end walls against the ends of casing 23. An insulating sleeve 3Ib surrounds end casing 29, which in a preferred form includes the brush holders and insulates that portion of the motor from side wall 23. Currentcarrying leads I6 extend from the motor through an opening 24h in rear wall 24 and are adapted to connect to a suitable source of current.

Referring to Figures 1 and 5, it is seen that impeller I3 comprises a plurality of radially extending blades 36 rigidly set at equal intervals in a single continuous-circle in vthe'conical outer surface of hub 3l, the plane of rotation of said blades being parallel to the base of the hub and perpendicular to motor drive shaft 32. The blades are pitched so that on rotation of the impeller in its operative direction air is induced to 'flowfrom the apex of and over the surface of=conicalhub Conical hub 3'I'is':

31 to and through duct I2'. rigidly fitted to the projecting end of motor shaft 32, its flat base facing and extending parallel to the outer surface of front Wall 21.

In the operation of a device constructedin ac"- cordance with the present invention the blower unit I is mounted on the exterior of wall .I I lof a conventional cabinet.. The intake orimpeller end of the unit is directed .toward the atmosphere exteriorto the cabinet. The discharge -ofthe duct' I2 'is directed into the cabinet and ltoward the electronic circuits positioned therein, The rotation .of impeller I3` by motor I5y inducesa iiow'ofrair from the atmosphere exterior to the cabinet over the surfaceof conicalhub .31`and into'duct I2.. Hub' 3l defiects the air owfrom anormal axial direction and directs it outwardly in a "pat-h' the limits of which approximate the projection of the hub'and the outer surface of motor'casing I 4.' In order that the expand-ing iiow ofair so produced 7.will not be constrained to `parallel'relationship upon entering. duct I2 the arcuate serrations I9 in the latter are cut sufficiently deep as not tointerfere with Ythe expanding'iiow of the llarger 'part of the air in` its movement into the cabinet andl over the components to be cooled. The advantage ofthe arcuate' serrations is two-fold, first, cooling 'eiiciency is increased because of the greater'areaof vcoverage vof the cabinet interior obtained by the continuing' expanding iiow of air, and; second,T by eliminating, as far as possible, all restriction' to free uninterrupted expanding' iiow;A the back pressure of the fan is reducedv to aminimum,'thus increasing fan efficiency.

While the particular apparatus hereirrs'liownA and described in detail is fully capable of attaining the objects and providing. the advantages hereinbefore stated, itis to be understood'that itis merely illustrative of the `presently.preferred embodiments ofthe invention and that 'nolimitations are intended to the `details'of construc= tion or design herein shown other than ascleined' inl'the appended claims.

I'c'laim':

1. In vanL axial-blower of the class described,- a'

cylindrical duct'formedwith a peripheraliiange at the frontend thereofT adaptedy to -afl'ixthe blower unitrigidly` to vthev wall 'of a conventional cabinet-'said duct being formedl withY arcuate'ser# rations 'in one end to "permit free owof an eX'- paridin'g 4'streamer-lair from's'aidduct, said duct beingnformed with a'plurality of arcuately'spaced' through' which said shaft extends; saidl end' platel having--v aV peripheraly shoulder seatingy the "front end of said cylindrical side Wall to close the front end of said housing and to position said motor relativetofsaid vside wall-'anditorsaidfductga multibladedrv impeller including y blades and'. a conical hub rigidly affixed to the projecting end of said Vmotor shaft with the apex thereof directed from said motor and housing, the blades of said impeller 'being arranged in a circular row on said hub .Y and pitched so that on rotation of the impelleriin-.litsoperative direction air is induced Vo'v'e'rftlfie apex'ofsaid hub, through the said blades, thenceover theremaining conical surface 0f said hub inan expanding ow, into and through said ductandithence out through the arcuate serrations in the discharge end of said duct. characterized lin that said serrations extend suiciently forwardly7 in said duct-thatama-,iorportionfof thefinduced air ow'isvf-reeto expandoradially immediately upon leavingzsa-id hub', andinlfthat the forward extensions-of said serrations are-in-l tersected `by an imaginary. projection of thcsurface of 4said conical surface of saidhub.

2. .Inf-an axialfblowerof the class describedya cylindricalduct yformed with -a peripheral ffl-ange at the-frontend .thereofI adapted tof.be..gafxed rigidly tothe outsidewall` of .-a-v conventional cabinet, they rear end .of said..cy1indrical 'duct being deeply crerielated,l said. d-uct `being-.formed with .fa plurality of webs :spaced midway between -adjacent crenelations .and at -the point of..maximum ductwall length, said. Webs lextend-ing.- radially from .theuinner surface of said-.duct toward its longitudinal. axis, an. venclosed :motor `housing sup,- portedby said webs concentrically withinlsaid duct, said .housing..including, a cylindricalmside wall .and detachable. front and... rear walls,y ysaid front wall .havinga..peripheral seat-adapted-to receive .the front endof said. cylindrical sidewalk..

a drive shaft `extended.lth'rough said front wall and positioned .relativeto said cylindrical.y side= wallvand to said .duct thereby, amultibIadedimpeller rigidly. aixed vtothe .projecting end--ofsaid drive shaft immediately. rforward of Ysaid. front.

wall, .said impellen having. a. .conical-hubhavinga .maximum diameter .substantially equal .to-.f the diameter `of .said housing. with -the .apex...thereof directed away from said housing. and.A havingv blades arranged in pitchedrelationshpinasngle continuous circular row on said hub; .said-construction being characterizedin. that .the "crenelations in said duct extend lsufiiciently,forwardlyfas.v

to .be 'intersectedby an` imaginary Aprojection .of

the conical surface of "said-hubinorder .toQprovida 

